Self-cleaning aperture tube for coulter study apparatus

ABSTRACT

A two chamber aperture tube for obtaining signals from particles suspended in a fluid which passes through a scanning aperture. The suspension enters the primary bore provided in one chamber and passes immediately to an inlet port or orifice in an elongate nozzle provided in the second chamber. The chambers are interconnected by conduits including a pump and filter such that flow of the suspension is continuous about a closed path to ensure that proper signals from all particles in the suspension are obtained.

United States Patent 1191 se [451 July 17,1973

[54] SELF-CLEANING APERTURE TUBE FOR 3,583,209 6/1971 Banks 73/432 PSCOULTER STUDY APPARATUS Primary Examiner-Rudolph V. Rolinec [75]Inventor. Walter R. Hogg, M1am1 Lakes, Fla. Attorney silveman & Cass[73] Assignee: Coulter Electronics Inc., Miami, Fla. 221 Filed: Apr. 7,1971 [571 ABSTRACT A two chamber aperture tube for obtaining signals[211 App] L923 from particles suspended in a fluid which passes througha scanning aperture. The suspension enters the [52] U.S. Cl. 324/71 CPprimary bore provided in one chamber and passes im- [51] Int. Cl. G0ln27/00 mediately to an inlet port or orifice in an elongate noz- [58]Field of Search 324/71 R, 71 CP; zle provided in the second chamber. Thechambers are 73/432 PS interconnected by conduits including a pump andfilter such that flow of the suspension is continuous about a [56]References Cited closed path to ensure that proper signals from allparti- D STATES A E cles in the suspension are obtained. 3,299,3541/1967: Ha 324/71 CP 11 Claims, 3 Drawing Figures 2a l 5 u ea? i v J I II 2 7 l". i 3 I B 6-" a: I .L 2' 1/ 7, a I in 9 r 50 l l (6 l I; 2:53am2*; 1 i

SELF-CLEANING APERTURE TUBE FOR COULTER STUDY APPARATUS CROSS-REFERENCETO RELATED PATENT BACKGROUND OF THE INVENTION 1. Field of the InventionThis invention relates generally to the art of studying the physicalproperties of particles carried in suspension and more particularly isconcerned with improved apparatus for obtaining signals from particlespassing through a scanning aperture without extraneous interference fromother particles.

2. Description of the Prior Art The structure disclosed in the RelatedPatent substantially decreases the possibility of undesirable spuriousparticle reading and count signals which occurred in prior art devices.This is accomplished by replacing the so-called aperture tube of priorart structures with a pair of chambers having an interconnection forseparating the electrical and mechanical effects of the particlespassing through the aperture. Particles passing through the aperture ofthe apparatus immediately are transported away from the proximity of theaperture so that there is little or no chance of spurious signalsresulting from said particles.

One of the objects of the invention disclosed in the Related Patent wasto provide an aperture tube which is self-cleaning in that thesuspension in the immediate vicinity of the aperture is kept free ofextraneous particles. As acknowledged in the patent, however, eddycurrents of fluid in the aperture tube at the downstream end of theprimary bore occurred, and these eddy currents swirled into thesecondary bore immediately adjacent the primary bore. It was believedthat the fluid would be stagnant liquid substantially devoid ofparticles, hence not introducing appreciable extraneous signals, butwhile this was largely true, the action was not sufficiently perfect tosatisfy the more critical demands of today's technology. A smallpercentage of particles were not caught by the orifice in the elongateneck of the second chamber and these sometimes produced extraneoussignals by virtue of the eddy currents at the bottom of the centralchamber of the aperture tube.

SUMMARY OF THE INVENTION To resolve the aforesaid problems with regardto extraneous signals, the present invention provides a selfcleaningaperture tube as disclosed in the related patent, with the addition of apump device interposed between the first and second chambers to producea closed system in which there are no inlets or outlets other than theprimary bore in the first chamber. The pump operates to draw theparticle suspension up through the second chamber and force the sameback into the first chamber, completing a circuit around this path andcreating a sheath flow at the orifice. The flow created by the pump issuch as to ensure that all particles introduced into the aperture tubeare caught by the orifice of the second chamber so as to prevent theoccurrence of extraneous signals.

Accordingly, the primary object of the invention is to provide animproved structure which ensures that all particles passing through theprimary bore are caught by the orifice provided in the second chamber ofthe aperture tube.

Other objects and advantages of the invention will occur to thoseskilledin this art as a description of the invention proceeds in connectionwith which a preferredembodiment is illustrated in the accompanyingdrawing and set forth in the accompanying specification.

BRIEF DESCRIPTION OF THE DRAWING The drawing is identical to that of theRelated Patent, except for those elements added thereto in accordancewith the invention herein.

FIG. 1 is a sectional view through the apparatus of the Related Patent,with the pump device and related elements of the invention illustratedin diagrammatic form.

FIG. 2 is a fragmentary enlarged sectional view through the apparatus inthe vicinity of the aperture.

FIG. 3 is a diagrammatic view of a device operating in connection withthe manometer-syphon having the improved invention associated therewith.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the following description,elements which are identical to those disclosed in the related patentare referred to herein by the same names and are indicated by the samereference numerals. Since the related patent is incorporated herein as apart hereof by specific reference, the disclosure thereof will not berepeated except in instances where understanding of the invention hereinwill be enhanced.

As illustrated in FIG. 1, a multiple chamber aperture tube or vessel 14comprising a first or central chamber 32 and a second chamber 34 issuspended within a vessel 10. In operation, the suspension 16 in vessel10 will flow through the aperture 12 and will, ideally, shoot directlyinto the orifice 40 and into the neck 36, to be carried thereafter alongthrough chamber 34, conduit 46, coupling 48, outlet conduit 50 and upbranch 52. In the structure of the Related Patent, the suspension wouldthen continue to discharge conduit 58 by way of passage 54 of stop-cock56.

In order to ensure that all particles in suspension 16 are caught byorifice 40 as they flow through aperture 12, the apparatus of theinvention includes apump and associated elements designated'generally bythe reference numeral 6, which elements have been interposed between thetwo chambers 32, 34. In the embodiment illustrated, a pair of Tjunctions 7, 8 have been spliced into branch 52 and conduit 62,respectively, so as to introduce the elements .6 into the flow systemrepresented by the solid line arrows throughout the aperture tube 14. Aconduit 2 leads through a filter 4 into pump 1 from junction 7, andconduit 3 leads out of pump 1 into junction 8.

It is to be understood that the points of entry 7, 8 into the twochambers 32, 34 could be made atariy point along the lengths thereof.The particular location shown is for illustrative purposes only.

The addition of the elements 6 to the system of the related patentproduces a closed system within the aperture tube 14 whereby, uponoperation of pump 1, suspension 16 is sucked through neck 36, up chamber34, and through conduits 46, 50 and 2. The suspension then passesthrough filter 4, where the particles suspended therein are removed, andinto pump 1. The particle free suspending liquid 16 is then forced backinto chamber 32 by way of conduits 3 and 62, completing a circuit aroundthis path and creating a sheath flow at orifice 40. The sample flow asdescribed in the related patent will be unaffected since this closedsystem has no other inlets or outlets.

Operation of pump 1 ensures that all particles in suspension 16 arecaught by the orifice 40 as they pass through aperture 12. The addedflow of clean suspension fluid, indicated by arrows in FIG. 2, servesfurther to sweep the region of secondary bore 22 free of all particleswhich are extraneous to those on which the sensing operation isperformed. By adjustment of the pump pressure, the sheath flow 5 will beof proper strength to ensure that all particles pass directly intoorifice 40.

The operation and functions of all remaining elements illustrated in thedrawing are the same as described in the related patent.

I claim:

1. in a particle measuring apparatus including a container ofparticulate liquid suspension to be tested, an aperture tube extendinginto said container, a vacuum source for moving the liquid from thecontainer into and through the aperture tube, a first electrode in thecontainer and a second electrode in the aperture tube to establish anelectrical field between said container and the aperture tube, and adetector, the aperture tube having a first and a second chamber, thefirst chamber having an aperture in communication with the liquidsuspension in the container, said second chamber having an orificeprovided therein at a point closely spaced from and directly oppositethe interior of said aperture, means connecting said second chamber tosaid vacuum source and means to'initially fill the first chamber withparticle free liquid and the second chamber with the liquid suspension,the improvement comprising, a conduit extending between said chambers toprovide a closed path for liquid flow therebetween, a pump interposed insaid conduit to create liquid flow about said path, and a filter memberin said conduit, whereby the suspension will flow from the containerthrough the aperture and the orifice into said second chamber to mixwith the liquid already therein and circulate about said path, saidfilter member removing the particles from the liquid before the same isreturned to the first chamber.

2. The structure as claimed in claim 1 in which an elongate neck extendsfrom the second chamber into the first chamber and said orifice isprovided in said neck.

3. An aperture tube for use in particle measuring apparatus including acontainer of particulate liquid suspension into which the aperture tubeextends, said tube including a first and a second chamber, the firstchamber having an aperture in communication with the liquid suspension,said second chamber having an orifice provided therein at a locationdirectly opposite the interior of said aperture, means for connectingsaid second chamber to an external source of vacuum, conduit meansextending between said chambers to provide a closed path for liquid flowtherebetween, a pump interposed in said conduit means to create liquidflow about said path, and a filter member in said conduit means, wherebythe suspension will flow through said aperture in the first chamber andthrough said orifice in the second chamber and then through said conduitand said pump and said filter member where the particles from thesuspension are removed before the same is forced into the first chamberand returned through said orifice.

4. An aperture tube as claimed in claim 3 in which an elongate neckextends from said second chamber into said first chamber and saidorifice is provided in said neck.

5. In a particle measuring apparatus which responds to the changes ofelectrical impedance due to the displacement of electrolyte by particlessuspended therein in an aperture which constricts an electric field,including a container of liquid suspension to be tested, a dualchamberaperture tube having a first and a second chamber extending into saidcontainer, a vacuum source for moving the liquid from the container intoand through the aperture tube, a first electrode in the container and asecond electrode in the aperture tube to establish the electric field,and a detector, the first chamber having an aperture forming acommunication between said container and said first chamber, the secondchamber having an orifice forming a communication between said first andsaid second chambers, said orifice being positioned close to anddirectly opposite said aperture, the improvement comprising, means forpreventing particles from the contents of the container from beingtransferred to suspension in the contents of the first chamber.

6. The structure as claimed in claim 5 in which said means comprise aconduit extending between said chambers to provide a closed path forliquid flow therebetween, a pump interposed in said conduit to createliquid circulation about said path, and a filter for removing particlesfrom the circulating liquid, such that the volume of liquid which flowsinto said orifice is the sum of the circulation about said closed pathplus the flow from said container into said first chamber.

7. The structure as claimed in claim 6 in which said vacuum source isadapted to withdraw liquid from the low pressure side of said pump.

8. The structure as claimed in claim 7 in which an elongate neck extendsfrom the second chamber into the first chamber and said orifice isprovided in said neck.

9. The structure as claimed in claim 7 in which filling means areprovided to fill the aperture tube, said conduit and said pump withliquid prior to performing the first test of particle suspensioncontained in said container.

10. The structure as claimed in claim 9 in which said filling meanscomprise a two-way stopcock and an open-close stopcock, said two-waystopcock being adapted to apply vacuum either to said first or saidsecond chamberor to neither, said open-close stopcock being adapted toconnect one chamber to a reservoir of suspension liquid.

11. The structure as claimed in claim 10 in which an elongate neckextends from the second chamber into the first chamber and said orificeis provided in said neck.

l t 0' i

1. In a particle measuring apparatus including a container ofparticulate liquid suspension to be tested, an aperture tube extendinginto said container, a vacuum source for moving the liquid from thecontainer into and through the aperture tube, a first electrode in thecontainer and a second electrode in the aperture tube to establish anelectrical field between said container and the aperture tube, and adetector, the aperture tube having a first and a second chamber, thefirst chamber having an aperture in communication with the liquidsuspension in the container, said second chamber having an orificeprovided therein at a point closely spaced from and directly oppositethe interior of said aperture, means connecting said second chamber tosaid vacuum source and means to initially fill the first chamber withparticle free liquid and the second chamber with the liquid suspension,the improvement comprising, a conduit extending between said chambers toprovide a closed path for liquid flow therebetween, a pump interposed insaid conduit to create liquid flow about said path, and a filter memberin said conduit, whereby the suspension will flow from the containerthrough the aperture and the orifice into said second chamber to mixwith the liquid already therein and circulate about said path, saidfilter member removing the particles from the liquid before the same isreturned to the first chamber.
 2. The structure as claimed in claim 1 inwhich an elongate neck extends from the second chamber into the firstchamber and said orifice is provided in said neck.
 3. An aperture tubefor use in particle measuring apparatus including a container ofparticulate liquid suspension into which the aperture tube extends, saidtube including a first and a second chamber, the first chamber having anaperture in communication with the liquid suspension, said secondchamber having an orifice provided therein at a location directlyopposite the interior of said aperture, means for connecting said secondchamber to an external source of vacuum, conduit means extending betweensaid chambers to provide a closed path for liquid flow therebetween, apump interposed in said conduit means to create liquid flow about saidpath, and a filter member in said conduit means, whereby the suspensionwill flow through said aperture in the first chamber and through saidorifice in the second chamber and then through said conduit and saidpump and said filter member where the particles from the suspension areremoved before the same is forced into the first chamber and returnedthrough said orifice.
 4. An aperture tube as claimed in claim 3 in whichan elongate neck extends from said second chamber into said firstchamber and said orifice is provided in said neck.
 5. In a particlemeasuring apparatus which responds to the changes of electricalimpedance due to the displacement of electrolyte by particles suspendedtherein in an aperture which constricts an electric field, including acontainer of liquid suspension to be tested, a dual-chamber aperturetube having a first and a second chamber extending into said container,a vacuum source for moving the liquid from the container into andthrough the aperture tube, a first electrode in the container and asecond electrode in the aperture tube to establish the electric field,and a detector, the fiRst chamber having an aperture forming acommunication between said container and said first chamber, the secondchamber having an orifice forming a communication between said first andsaid second chambers, said orifice being positioned close to anddirectly opposite said aperture, the improvement comprising, means forpreventing particles from the contents of the container from beingtransferred to suspension in the contents of the first chamber.
 6. Thestructure as claimed in claim 5 in which said means comprise a conduitextending between said chambers to provide a closed path for liquid flowtherebetween, a pump interposed in said conduit to create liquidcirculation about said path, and a filter for removing particles fromthe circulating liquid, such that the volume of liquid which flows intosaid orifice is the sum of the circulation about said closed path plusthe flow from said container into said first chamber.
 7. The structureas claimed in claim 6 in which said vacuum source is adapted to withdrawliquid from the low pressure side of said pump.
 8. The structure asclaimed in claim 7 in which an elongate neck extends from the secondchamber into the first chamber and said orifice is provided in saidneck.
 9. The structure as claimed in claim 7 in which filling means areprovided to fill the aperture tube, said conduit and said pump withliquid prior to performing the first test of particle suspensioncontained in said container.
 10. The structure as claimed in claim 9 inwhich said filling means comprise a two-way stopcock and an open-closestopcock, said two-way stopcock being adapted to apply vacuum either tosaid first or said second chamber or to neither, said open-closestopcock being adapted to connect one chamber to a reservoir ofsuspension liquid.
 11. The structure as claimed in claim 10 in which anelongate neck extends from the second chamber into the first chamber andsaid orifice is provided in said neck.